You just connect to an IRC network and join any random name you want and the channel is automatically created. However is is recommended that you register the channel afterwards with chanserv to ensure you retain moderation rights to it.
Why would you want to bother creating a room on outmoded, antiquated and obsolete IRC? Haven't you heard of Discord?
You're being heavily downvoted because this instance is "a community of free software and privacy enthusiasts" as the title on the front page suggests, and this in particular is the !opensource@lemmy.ml community. Discord is the complete antithesis of this, as it is a proprietary application locked to a centralized server that also spies on its users.
What is wrong with Discord (Richard Stallman)
Spyware level: Extremely High (Spyware Watchdog)
That being said, there are modern alternatives to IRC, such as Matrix, XMPP, Zulip, Mattermost, or RocketChat. However, I think IRC is fairly good at what it does.
Why would you want to bother creating a room on closed, proprietary and non-federated Discord? Haven't you heard of Matrix?